Spectrometry techniques can be used to identify the presence of a target chemical species, or analyte, in a gas sample. Spectrometry techniques commonly rely on the interaction of the analyte with light, either in the visible spectrum or at wavelengths that cannot be seen. Depending on the spectrometry technique used, the spectra collected may show the intensity of light absorbed, light emitted, or light scattered from a sample after an exciting beam of light passes through the gas sample. Peaks or dips in the spectral profile of the received light intensity can be indicative of particular chemical species. In some spectrometry techniques, quantities or relative amounts of each chemical species can be derived from the spectra. However, if insufficient amounts of light from the gas sample are collected by a spectrometer, then the spectra may yield no useful data, or can result in noisy data. Noisy data can be inconclusive and meaningful information can be difficult to obtain from such data.
Variations in environmental conditions, aging or fouling of reflector surfaces in a spectrometer sample cell, or replacement of fouled or deteriorated reflector surfaces can cause a beam path of a light and/or a beam profile of a light and/or intensity of a light from a light source within a spectrometer to change. The change can occur over time or as a result of changing a reflector. Changes of the beam path in an optical spectrometer can reduce the amount of light available for analysis from the sample cell. Furthermore, changes of a beam path can cause an offset from calibration of the spectrometer, especially for optical absorption spectroscopy, where absorption of light follows the Beer-Lambert law
      (          T      =                        I                      I            0                          =                              e                          -                              ∑                l                                              =                                                    e                                                      -                    σ                                    ⁢                                                                          ⁢                  lN                                            ⁢                                                          ⁢              or              ⁢                                                          ⁢              A                        =                          -                              ln                ⁡                                  (                                      I                                          I                      0                                                        )                                                                          )    ,scaling exponentially with path length. Changing or repairing the sample cell in a spectrometer can require calibration or alignment of spectrometry system by a skilled technician. Such service calls and factory repairs are costly and result in downtime for the spectrometer and the operation it controls.